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ELECTRONIC TIMER Filed July 30, 1945 United States Patent Otitice2,803,814 Patented Aug. 20, 1957 ELECTRONIC TIMER Dwight Wilson Bloser,West Englewood, N. J., assignor to Bendix Aviation Corporation,Teterboro, N. J., a corporation of Delaware Application July 30, 1945,Serial No. 607,736

36 Claims. (Cl. 340-234) This invention relates to electrical timingapparatus, and particularly to that type of timing apparatus wherein aseries of load devices are sequentially operated for a predeterminedtime and there is automatically provided a predetermined interval oftime between cycles of operation.

An object of the invention is to provide improved electrical timingapparatus `controlled by the charged condition of a capacitor orcondenser.

Another object of the invention is to provide a novel circuit foreffecting a charging operation of the timing condenser through a diodeso as to eliminate all unnecessary switch contacts and wearing parts.

Another object of the invention is to provide a novel circuit in whichthe charging operation of a timing condenser may be eiected through adiode and the electronic valve controlled thereby.

Another object of the invention is to provide a resistor connecting thetiming condenser to the source of electrical energy during the chargingoperation and applying a positive bias to the cathode of the controlledtube so as to ldeionize the tube during the latter charging operation.

Another object of the invention is to provide a resistor connectedacross the plate and cathode of an electronic Valve so as to control theinductive voltage rise across a coil in the plate circuit so as toeffect a greater time delay than would normally be obtained with thetime constant and voltage of the main electronic supply source.

Another object of the invention is to provide novel manually operablemeans for selecting the interval of time between cycles of operation ofthe same.

Another object of the present invention is to provide novel electricalmeans for timing the periods of operation of an electric motor.

Another object of the invention is to provide improved timing apparatusfor controlling the periods of inflation of a series of solenoidcontrolled inflatable elements or boots for preventing the accumulationof ice on or the removal of ice from aerofoil surfaces of an aircraft.The latter 1system of inflatable elements may be of the type -describedand claimed in the copending applications Serial Numbers 498,248 ofDonald M. Lawrence, David Gregg and Myron L. Taylor, filed August 11,1943, now U. S. Patent No. 2,515,519, and application Serial Number498,250 of Myron L. Taylor, William B. Pond and Herbert A. Eayrs, filedAugust 11, 1943, now U. S. Patent No. 2,444,208, and all of whichpatents have been assigned to Bendix Aviation Corporation.

These and other objects and features of the invention are pointed out inthe following description in terms of the embodiment thereof which isshown in the accompanying drawings. It is to be under-stood, however,that the drawings are for the purpose of illustration only, and are notdesigned as a definition of the limits of the invention, reference beinghad to the appended claims for this purpose.

. In the drawings:

Figure 1 shows a plan view of the control panel and indicator lights ofthe present invention;

Figure 2 represents an electrical timing circuit embodying certainfeatures of my invention;

Figure 3 is a view of the circuit of Figure 2 with certain-non-pertinent elements omitted and showing the electron ilow during thecharging operation of the tim` ing condenser by solid arrows, while theelectron ow' during the discharging operation is indicated by dottedarrows;

Figure 4 is a view of a modified circuit from Figure 3 with thenon-pertinent elements omitted and showing the electron ow during thecharging operation by solid arrows and the electron flow during thedischarging operation by dotted arrows;

Figure 5 represents an electrical timing circuit embodying a third formof the invention, including an electric motor.

Referring now to Figure 2, there i-s shown a system for timing theoperation of a stepper relay 10 which controls the energization of aseries of loads 11, indicated as a plurality of electromagnets. Theelectronic timer is particularly adapted for use in conjunction with themanifold type of inflatable ice eliminating systems described in t-heaforenoted copending applications. The electromagnets 11 may serve uponenergization to open the boot-inflating valves automatically in theproper sequence and for proper time intervals.

The stepper relay 10 may be of a conventional type comprising anelectromagnetic winding 12 which controls the movement of an armature 13pivotally supported at 14. A ratchet arm 15 is pivotally mounted on thearmature 13 and is biased into engaging relation with a ratchet wheel 16by a spring 17. A second spring 18 biases the armature 13 in acounterclockwise direction into contacting relation with a stop 19. Apawl 20 is biased into engaging relation with the teeth of the ratchetwheel 16 by a spring 21 so as to prevent rotation of the ratchet wheel16 in a counterclockwise direction.

It will be readily seen from the foregoing that upon energization of theelectromagnet 12 the armature 13 will be pivoted in a clockwisedirection in opposition to the force of the spring 18 causing theratchet arm 15 to engage the next succeeding tooth of the ratchet wheel16. At the extreme limit of movement of the armature 13 an actuatingmember 22 carried thereby engages the free end of a leaf spring 23 so asto open the contacts of a switch 24.

The opening of the switch 24 breaks the circuit of the electromagnet 12,as will be explained hereinafter. causing de-energization of theelectromagnet 12, whereupon the spring 18 actuates the armature 13 in acounterclockwise direction causing the pawl 15 to impart an increment ofmovement to the ratchet wheel 16 in a clockwise direction.

The ratchet wheel 16 is connected through a suitable shaft 25 indicatedherein by dotted lines to switch arms 26, 27, 28 and 29.

The switch arms 26, 27 and 28 are each arranged to contact in successiona series of contacts 26A-L, 27A-L and 28A-L. The switch arms 26, 27 and2S move from one contact to the next succeeding contact for eachincrement of movement imparted to the ratchet wheel 16 by the stepperrelay 10 and upon one end of the switch arm moving out of contactingrelation with the contact K the opposite end closes the contact L.

The switch contacts 26A-K are connected through suitable electricalconductors 30A-K, respectively to one terminal of corresponding loaddevices or electromagnets 11. The opposite terminal of theelectromagnets 11 are .conductor 34 which leads to a switch contact 35controlledby a switch 36. The switch 36 is connected by a conductor 37through an electric light or indicator 38 to the negative terminal ofthe source of electrical energy 32.

There may also be connected in parallel to the electromagnets 11suitable indicator lights 39A-K for each load device or boot operatingsolenoid. The latter lights may be mounted on the panel of the timer ormay be preferably provided in a separate unit as indicated in Figure 1.There is also provided a light 39L connected to the contact 26L byconductor 30L. Another light 39M is connected to the main energizingcircuit by conductor 30M as will appear. The lights 39A-M are connectedby conductor 31A to the conductor 31 through a switch 31B.

As will be explained, the light 38 is arranged so as to indicate thetimer is in operation, while the lights 39A-L will indicate theparticular load device or ice eliminating boot in operation. Thelight'39M indicates whether the system is energized.

l The switch arm 36 is arranged so that it may alternatep be provided asdesired.

The contact 26L is not connected to the load devices 11, soA that uponthe switch arm 26 contacting the same, the circuit to all of the loaddevices 11 are open for a purpose which will appear hereinafter.

The switch arm 27 is arranged to successively close contacts 27A-L. Thelatter contacts are interconnected by an electrical conductor 42 to aconductor 43. The

conductor 43 is connected to the positive terminal of the source ofelectrical energy 32 through a conductor 43A so as to complete thecircuit for the light 38, lights 39 and Vthe load devices 11.

The switch arms 27 by opening the contacts 27A-K in unison with theopening of contacts 26A-K by the switch arm 26 is arranged to reduce thearcing at contacts 26A-K by providing a series break. Similarly theswitch arm 27 in opening the contacts 27A-L causes flickering of thelight 38 which will indicate to the operator that the system is inoperation.

There also leads from the conductor 43 a conductor 45 which leads tomanually operable switches 46, 47, 48, 49 Land 50 connected in seriesand arranged to close respectively contacts I-K, H-G, E4F, D*C and A-Bconnected through suitable conductors to the circuits controlling theload devices or solenoids 11. The switches 46, 47, 48, 49 and 50 thusprovide manually operable means for controlling energization of the loaddevices or ice eliminating boot operating solenoids 1l. It will benoted, moreover, that since the latter switches are connected in seriesonly one of the set of load devices may be energized at a time, throughoperation of the manual switch means. The latter arrangement thusprevents an overload from being inadvertently applied to the iceeliminating system.

The switch arm 28 is arranged to sequentially close contacts 28A-Lconnected to suitable resistor elements 51 for a purpose which will beexplained hereinafter.

The shaft also drives a switch arm 29 arranged to actuate an oi normalswitch 52 to an open position upon the switch arms 26, 27 and 28 beingpositioned so as to close the respective contacts 26L, 27L and 28Lrespectively. Upon the switch arms 26, 27 and 28 being adjusted intocontacting relation with one of the other contacts, the member 29 isadjusted out of contacting relation with the otnormal switch 52 soy asto permit the switch 52 to close for purposes which will be explained.

The winding 12 of the stepper relay 10 has one terminal connected by anelectrical conductor 53 to conductor 43A and thus to the positiveterminal of the source of electrical energy 32. The opposite terminal ofthe winding 12 is connected by an electrical conductor 54 to an anode orplate 55 of an electronic valve 56.

The electronic valve 56 has a cathode 57, a control grid 58, a cathodeshield grid 59, a heater or iilament 60 and the plate 55.

The cathode 57 is connected by a conductor 61 to one contact of the olfnormal switch 52 while the opposite contact of the off normal switch 52is connected by a conductor 62 to one contact of the switch 24. Theopposite contact of the switch 24 is connected by a conductor 63 to thenegative terminal of the source of electrical energy 32.

The conductor 62 also leads to one contact of a push pull switch 64. Theopposite contact of the switch 64 is connected by a conductor 65 to theconductor 61 through a contact 66 and adjustable switch arm 67. Thus itwill be seen that the cathode 57 may be connected to the negativeterminal of the source of electrical energy 32 by closing the push pullswitch 64 upon the switch arm 67 being adjusted to a position closingcontact 66.

.The switch arm 67 is mechanically connected to switch arms 68, 69, 70and manually adjustable knob 71 through a shaft 72 for a purpose whichwill be explained hereinafter.

Other contacts controlled by the switch arm 67 include contact 72 whichis an open contact and three contacts 73 which are electricallyconnected by a conductor 74 to the conductor 62. Thus the negativeterminal of the source of electrical energy 32 may be connected to thecathode 57 upon the switch arm 67 closing one of the contacts 73.

The electron flow from the cathode 57 to the plate 55 is controlled by agrid 58 connected by a conductor 75 to one end of a resistor 76. Theopposite end of the resistor 76 is connected by a conductor 77 to aplate 78 of a condenser 79. The opposite plate 80 of the condenser 79 isconnected by a conductor 81 to the conductor 61.

The plate 78 is connected through a conductor 82 to the switch arm 28previously described and which is arranged to close sequentially thecontacts 28A through L.

Leading from the contacts28A through L, respectively are resistors 51A-Leach of a value suicient to elect a predeterminedtime interval forenergizing the load device 11 .corresponding thereto. The resistors51A-L may be of different value so as to effect different time intervalsof operation for each load device.

Leading from Vthe opposite terminals of the resistors 51A-L is aconductor 83 which leads to the conductor 43. Connected to the conductor43 are four contacts 84 and there is provided a switch arm 70 forclosing the same. The conductor 43A connects the switch arm 7 0 to thepositive terminal of -the source of electrical energy 32. Cooperatingwith the switch arm 70 is a fth and open contact 86. Leading from thecontacts 84 is a conductor 87 which connects the same to the switch arm69. The conductor 87 also connects the light 39M to the positiveterminal of the source of electrical energy 32 through arm 70.

The switch arm 69 is arranged to selectively contact one of ve contactsincluding two open contacts 88 and three contacts 89 connected by anelectrical conductor 90 to the resistor 51L at a point intermediate theopposite ends of the latter resistor.

It will be seen then that when the switch arm 69 closes one of thecontacts 89 a portion of the resistor S1 leading from the contact 28Lwill be shunted out of the circuit leading from the positive terminal ofthe source of electrical energy 32 and the plate 78 of the condenser 70.However, upon the switch arm 69 contacting one of the open contacts 88and the switch arm 70 closing one of the contacts 84 the full resistanceof the resistor S1 leading from the contact 28L will be inserted in thelatter circuit.

The switch arm 68 is arranged to selectively contact one of the' fivecontacts including four open contacts 91 and one contact 92 from which aconductor 93 leads to the conductor 82. A conductor 94 leads from theswitch arm 63 to the plate of a second condenser 9S. The op'- positeplate of the condenser 95 is connected to the conductor 81. Thus uponswitch arm 68 closing contact 92 Ithe condenser 95 is connected inparallel to condenser 79 so as to increase thel total condensercapacity.

Upon the switch arm 68 being adjusted so as to open the contact 92, itwill be seen that condenser 79 only will apply the controlling bias onfthe grid 58.

The condenser 79 or condensers 79 and 95 are charged through operationof a diode 100 having an anode 101, cathode 102 and heater or filament103. The anode 101 is connected by a conductor 104 to the conductor 82leading to the plate 78 of condenser 79. The cathode 102 is connected bya conductor 105 leading to the negative terminal of the source ofelectrical energy 32.

The conductor 105 also leads to a resistor 106 through which theconductor 105 is connected to one terminal of the heater or lament 60 ofthe electronic valve S6. The opposite terminal of the filament 60 is-connected by a conductor 107 to one terminal of the heater or filament103 of the diode 100. A conductor 108 connects the opposite terminal ofthe filament 103 to the conductor 43. Through the conductor 43, .switchcontacts 84, and switch arm 70, the conductor 108 is connected to thepositive terminal of the source of electrical energy 32.

The shield grid 59 is connected to the negative terminal of the sourceof electrical energy 32 by a conductor 110 leading to the conductor 105.There is connected between the anode 55 and the conductor 110 a resistor111 to limit the rise of induced voltage that occurs across the stepperrelay coil 12 as its field decays. By proper choice of the resistor 111the same may be so arranged as to allow a controlled voltage rise tooccur which will be reflected in a higher charge voltage on thecondenser 79 with a corresponding increase in the time of discharge forthe same resistor 51, capacitor 79 and line voltage combination.

Operation The foregoing electronic timer is particularly designed foruse in conjunction with the manifold type of ice eliminating system forairfoil surfaces of aircraft and is arranged to open the boot inflatingvalves automatically in the proper sequence for the proper timeintervals. Since ice does not form at the same rate or to the samedegree on all occasions, a certain flexibility of control has beenincorporated to permit the operator to vary certain components of thesystem to suit the prevailing conditions.

As shown in Figure l, the control system may be mounted o-n a controlpanel A which is preferably mounted in the Engineers Compartment of :theaircraft, while the indicator lights 39A-M and switch 31B are carried bya separate unit B. The unit B is electrically connected with the controlpanel A through a conduit C as indicated in Figure 2 and the unit B ismounted apart from the control panel A. The unit B is preferably mountedin the pilots compartment of the aircraft.

It will be seen, moreover, that the panel A has mounted thereon thesingle control knob 71, indicator light 38 and I the emergency flipswitches A-K for manually controlling the operation of the inflatableice eliminating elements or boots.

Starting with the knob 71 in single cycle position as shown in Figure 2with switch arm 67 on contact 66, switch arm 68 on contact 91, switcharm 69 on contact 89 and switch arm 70 on contact 84, operation of thesystem is initiatedA by closing single cycle button or switch 64,

whereupon the electronic valve 56`fires energizing thel stepper relaycoil 12 and drawing up the ratchet arm 12 until it engages the nexttooth on ratchet wheel 16 and simultaneously opens interrupter switch24. The opening of the interrupter switch 24 breaks the circuit betweenthe negative terminal of the source of electrical energy 32 andthecathode 57 of the electronic valve 56.

Electronic flow continues through the valve 56 for part of the open timeof interrupter switch 24 so as to charge the condenser 79. The chargingcircuit is shown in Figure 3 in which certain of the non-pertinent partsof the system have been omitted for clarity of illustration.

The electronic flow during the charging action as indicated by solidarrows in Figure 3 is from the plate 80 of the condenser 79 though theelectronic valve 56, from the cathode 57 to the plate 55, and throughrelay coil 12 to the positive terminal of the source of electricalenergy 32. The opposite plate 78 of the condenser 79 is negativelycharged by an electronic flow from the negative terminal of the sourceof electrical energy 32 through the diode 100.

Plate 78 of condenser 79 is also connected by means of conductor 82 andresistance 51 to the positive side of the source of electrical energy32, but since the resistance of diode 100 to electron flow in thecharging direction is negligible compared to resistance 51, essentiallythe full line voltage is impressed across the condenser 79. The diode100 therefore, acts in the nature of a switch contact on charging toconnect plate 78 of condenser 79 to the negative side of the source ofelectrical energy 32.

lt will be noted that the resistor 111 serves to limit the rise ofinduced voltage that occurs across the stepper relay coil 12 as itsfield decays. By a proper choice of this resistor 111 there may beallowed a controlled voltage rise to occur that will be reflected in ahigher charge voltage on the condenser 79 with a corresponding increasein the time of discharge for the same resistor 51, capacitor 79 and linevoltage combination.

The condenser 79 is charged for a time interval determined by theimpedance of the coil 12 in the charging circuit until the control grid58 becomes biased sufficiently negative with respect to the cathode 57,because of the charge on the condenser 79, that electronic flow throughthe electronic valve 56 ceases and the stepper relay coil 12 becomessufficiently deenergized as to release the switch 24. After the chargingof the condenser 79, the remainder of the open time of the interrupterswitch 24 allows the electronic valve 56 to deionize. Uponde-energization of the relay coil 12 following the opening of the switch24 and charging of the condenser 79, the spring 18 draws the ratchet arm15 downward driving through the ratchet wheel 16, contact arms 26, 27and 28 so as to close contacts 26A, 27A and 28A, while off normal switcharm 29 is moved to a position out of contacting relation with switch 52so as to permit the same to close the circuit between the cathode andinterrupter switch 24. The downward movement of the ratchet arm 15 hasalso closed interrupter switch 24 so that the negative terminal of thesource of electrical energy 32 is now connected through switches 24 and52 to the cathode 57.

The condenser 79 has now been charged and provides a negative bias onthe control grid 58 to prevent further firing of the electronic valve 56until the condenser 79 has been discharged.

As shown in Figure 3, the condenser 79 discharges as indicated by dottedarrows. The electron charge applied to the plate 78 of condenser 79flows through switch arm 28 and resistor 51 to the positive terminal ofthe source of electrical energy 32, while there is electronic flow fromthe negative terminal through the closed switch 24 to the plate 80 ofthe condenser 79. The duration of the discharge period will, of course,be dependent upon the value of the resistor 51 in the discharge circuit.

There is no electron flow through diode during discharge, since theplate of the diode 100 is connected Vto. the `negatively charged plate78 of the condenser 79 4ridftliecathhde is connected to positivelycharged plate The diode 100 therefore, acts in the nature' of a switchon discharging to disconnect plate 78 of condenser 79 from the negativeside of the source of electrical energy -32. Thus it will be seen thatthe diode 100 acts to replace a pair of contacts that would otherwise benecessary for connecting and disconnecting plate 78 of the condenser 79for charging and discharging, respectively.

While I have shown a diode as applied to the foregoing, it will bereadily seen that any unidirectional current device such as a dry platerectifier or liquid electrolytic rectifier may be used. However, a diodeis preferable since the same has infinite resistance to reverse How.

` After the elapse of a predetermined interval of time Aduring whichYthe condenser 79 discharges, as indicated,

ing the switch contacts 26L, 27L and 28L the circuit to the load devices11 is open and the ofi normal switch arm 29 once again opens the switch52 in the cathode circuit.

Under the single cycle operation the timer causes each boot to beinflated in turn once, after the starting button 64 is depressed andthen waits until the starting button 64 is again depressed beforeproceeding with another intlation cycle. This operation is useful underlow rate icing conditions.

Continuous operation may be effected by adjusting the knob 71 so as toposition switch arm 67 so as to close one of the contacts 73. The switcharm 67 will then shunt the single cycle switch 64 so that continuousoperav tion may be effected,

will be seen that since contact 88 is an open Contact the conductor 90will be cut out of operation.

However, since switch arm 70 closes contact 84 to which conductor 83 isconnected through conductor 43, it will be seen that the full resistanceof resistor 51L will be connected into the discharge circuit of thecondenser 79 so that the electronic valve 56 will be held from firinguntil the condenser 79 has discharged sufiiciently. The latter intervalis shown as a sixty second dwell, but the period may be for a greater orless period as` determined by the value of the resistor 51L.

After the condenser 79 has discharged the electronic Avalve 56 tires andthe operation of the system repeats.

Under the latter adjustment of the knob 71 the timer Vcauses thesequential intiation of each of the ice eli-minating boots in turn,waits sixty seconds or such other predetermined period and then repeatsuntil the timer is turned off. This operation is preferable undermediumrate icing conditions. If the knob 71 be adjusted so as to causeswitch arm 67 to close `one of the contacts 73 and the switch arm 69 toclose one of the contacts 89, it will be seen that only a portion of theresistor 51L will be connected into the discharge conduit of thecondenser 79 through conductor 90 so that the delay period betweencycles of operation may be imperceptible or approaching zero seconddwell.

In the latter operation, the timer keeps repeating the inflating cyclesjust as in the previous operation, but docs not delay between successiveinflation cycles. The

latter operation is adapted for high rate icing conditions.

Should it be desired to increase the intiation period for l each boot,this may be accomplished by adjusting the V79. The'latter adjustmentwill also cause adjustment ofswitch arm 67 to'close contact 73, switcharm 69 to close contact 89 and switch arm 70 to close contact`84.

By thus connecting the condenser in parallel to the condenser 79"theperiod of inflation for each boot may be increased for example by ftypercent or any other predetermined amount.

In this operation, the cycling is repetitive without delay betweencycles, but the ination period for each boot is increased for example byfifty percent,

This operation is particularly effective under high alti tude conditionsand sub-normal air flows from the engine arr pump.

As a safety fall-back there are provided a row of auxiliary handoperated switches 46, 47, 48, 49 and 50 connected so as to directlycontrol the inflation andderlation of the several boots.

The timer may be cut off by adjusting the knob 71 so as to cause switcharms 67, 68, 69 and 70 to contact the `open contacts 72, 91, 8S, and 86respectively.

Modified form of Figure 4 In Figure 4 there is shown a modified form ofthe invention which differs from the form shown in Figure 2 in theprovision of a resistor 112 connecting the plate 80 of the condenser 79directly to the positive terminal of the source of electrical energy 32.

Under the latter arrangement the condenser 79 charges through the diodeand resistor 112 rather than through the electronic valve 56. Under thelatter arrangement the valve 56 is directly deionized through theresistor 112 during the charging operation. The charging and dischargingcircuits are indicated in Figure 4 by solid and dotted arrowsrespectively.

There is further provided a condenser 113 connected in parallel to thestepper relay coil 12 for momentarily maintaining the coil 12 energizedupon the switch 24 openmg.

The operation of the form of the invention of Figure 4 is otherwisesubstantially the same as described for the form of Figure 2 andtherefore a further detail description is not believed necessary.

Modified form of Figure 5 In the modified form of the invention shown inFigure 5, there is provided a motor in the plate circuit instead of thestepper relay coil 12. The motor 120 has an armature 121 and lieldwinding 122 connected to the plate 55 by conductor 54 and to thepositive terminal of the source of electrical energy by the conductor53.

The armature 121 drives a shaft 123 indicated by dotted lines to whichthere is atiixed a cam 124 and gear 125 driving a gear train 126 whichconnects the shaft 123 to a second shaft 127 to which there is affixedthe switch arms 26 and 28, as shown, together with a second cam 128.

The came 128 operates an oli? normal switch 52 connected across theswitch 64 previously described with reference to Figure 2, while the cam124 operates a switch 130 having make before break contacts in which acontact 131 is normally closed by a switch arm 132 having a contact 13'3normally open in relation to a second switch arm 134. The cam 124 has acam surface 135 so arranged that upon initial energization of the motor120 and rotation of the shaft 123 the switch arm 134 is actuated so asto first close the switch contact 133 and then actuate the switch arm132 so as to open the contact 131. Upon continued rotation of the shaft123 the surface causes the switch arm 134 to actuate the switch arm 132so as to first close contact 13'1 before the switch arm 134 opens thecontact 133.

The switch arm 132 and contact 133 are connected to conductor 61 leadingto the negative terminal of the 9 source of electrical energy 32 throughthe off normal switch 52 or the switch 64 and conductor 62..

The contact 131 is connected by a conductor 131A leading to Ithe cathode57. The switch arm 134 is connected to a conductor 136 leading to theconductor 54 which connects the plate 55 and the :motor 120 aspreviously described. A conductor 13'7 leads from the conductor 13.6 toa contact 138 controlled by the switch arm. 67.

In the operation of the latter modified form of the invention whenelectronic valve 56 fires either upon clos- V'ing switch 64 or upondischarge of the condenser 79 connected across the cathode 57 and grid58, a circuit 'is completed from the negative terminal of the source ofelectrical energy 32 through conductor 62, switch 64, or switch 5,2,conductor 61,switch 130, conductor 131A, cathode 57, plate 55, conductor54, motor 120, and conductor 53 returning to the positive terminal ofthe source of electrical energy 32. The motor 120 rotates in acounterclockwise direction driving the cam 124 so as to causekswitch arm134 of switch 130 to close contact 133 whereupon the electronic valve isshunted through conductor 136 and the motor is energized throughconductor 136. Continued rotati-on causes switch arm 134 to actuateswitch arm 132 so as lto open contact 131.

Upon opening the contact 131 the condenser 79 is charged by anelectronic flow from the negative terminal of the source of electricalenergy 32, through the diode 100 tothe plate 78, and from the plate 80through the resistor 1 12 to the positive terminal as previously eX-plained with reference to the form of Figure 4.

Energization of the motor 120 causes shaft 123 to continue to rotateuntil cam 124 once again causes switch arm 134 to actuate arm 132 so asto close contact 131 and cause arm 13410 open contact 133 at which pointthe arms 26 and 28 have been adjusted through shaft 127 and gear train126 to the next succeeding contact. Since `condenser 79 is now charged,a negative bias will be applied to the grid 58 by the condenser 79preventing the tube 56 from tiring until the condenser 79 has dischargedthrough the resistor 51, as previously explained with reference to theforms of Figures 2 and 4. The operation then repeats until the shaft 123driven by the motor 120 causes the switch arms 26 and 28 to contact thecontacts 26L and 28L, respectively at which point the cam 128 causes theoff normal switch 53 to open.

If the switch arm 67 is set at single cycle operation by adjustment soas to close contact 66, then of course the operation ceases untilstarted again by closing switch 64, but if the switch arm 67 is adjustedfor automatic operation as shown in Figure 5, then the operation repeatsupon the condenser 79 discharging through the resistor 51L. Y

The switch arms 67, 68, 69 and 70 may be mechanically connected togetherso as to operate from a single manually adjustable knob 71 as previouslydescribed with reference to Figure 2, or the same may be separatelyoperable so as to vary the effects produced thereby.

In the case of switch arm 67, it will be noted that upon the sameclosing contact 138 as in the off position, motor 120 will drive withoutdelay shafts 123 and 127 until cam 128 opens the off normal switch 52.During the latter operation, with switch arm 70 turned to its offposition in which it contacts the open contact 86, the boot Valveoperating solenoids will not be energized.

Although only three embodiments of the invention have been illustratedand described, various changes in the form and relative arrangements ofthe parts, which will now appear to those skilled in the art, may bemade without departing from the scope of the invention. Reference is,therefore, to be had to the appended claims for a definition of thelimits of the invention.

y What is claimed is:

1. A time delay circuit controlling apparatus compris- .ins anelectronic valve having an anode and cathode connected in said timedelay circuit and a control grid, a capacitor connected between the gridand the cathode, electromagnetic means connected in said time delaycircuit and energized upon said valve closing said time delay circuit, asecond circuit for charging said capacitor and a third circuit fordischarging said capacitor, a switch member in said time del-ay circuitand said third circuit, said Iswitch member opened by saidelectromagnetic means upon the energization thereof, a diode in thesecond charging circuit for said capacitor and effective upon theopening of said switch member to complete the charging circuit for saidcapacitor, and s-aid electromagnetic means arranged to close said switchmember after the charging of said capacitor, a resistor effective uponthe closing of said switch member to complete the third circuit fordischarging said capacitor, said capacitor arranged upon discharging tosupply a negative bias to said grid for restraining said electronicvalve from closing said time delay circuit, the resistor in said thirdcircuit retarding the discharge of said capacitor whereby said capacitorcontinues to apply a negative bias to said grid for a predetermineddelay period so as to restrain said electronic valve from closing saidtime delay circuit during said delay period.

2. A time delay circuit controlling apparatus comprising an electronicvalve having an anode and cathode connected in said time delay circuitand a control grid, a capacitor connected between the grid and thecathode, charging and discharging circuits for said capacitor,electromagnetic means controlled by said time delay circuit foralternately elfecting said charging and discharging circuits for saidcapacitor, means in said charging circuit conductive to electronic flowin one direction only, said capacitor supplyin-g a bias to said gridduring the discharge thereof for controlling the operation of saidvalve, variable means for retarding the discharge of said capacitor, andsaid variable means controlled by said electromagnetic means.

3. A time delay circuit controlling apparatus comprising an electronicvalve having an anode and cathode connected in said time delay circuitand a control grid, av

capacitor connected between the grid and the cathode s o as to controlsaid valve, charging and discharging circuits for said capacitor, anelectromagnetic winding in said time delay circuit for alternatelyeffecting said charging and discharging circuits, a source of electricalenergy for said circuits, and said charging circuit including saidelectronic valve, said electromagnetic winding, and a resistor connectedbetween the anode of said electronic valve and the negative terminal ofthe source of electrical energy, said resistor providing means forcontrolling the inductive voltage rise across the electromagneticwinding upon the opening of the time delay circuit.

4. A time delay circuit controlling apparatus comprising an electronicvalve having an anode and cathode connected in said time delay circuitand a control grid, a capacitor, charging and discharging circuits forsaid capacitor, said capacitor so arranged as to supply a bias to saidgrid during electronic discharge therefrom, means including anotherelectronic valve in the charging circuit conductive to electronic flowin the ch-arging direction only, said iirst mentioned electronic valveconnected at One side of said capacitor and the other electronic valveconnected at the opposite side of said capacitor, said electronic valvesserially connecting said capacitor in Said charging circuit, andelectromagnetic means controlled by said time delay circuit foralternately effecting said charging'and discharging circuits for saidcapacitor.

5. A time delay circuit controlling apparatus comprising anelectronic'valve having an anode and a cathode connected in said timedelay circuit and a control grid, a capacitor for controlling theoperation of said electronic valve, a source of electrical energy, firstmeans connecting said source in circuit with said capacitor for chargingthe same, second means including a switch in said time delay circuit andconnecting said source in circuit with said capacitor for dischargingthe same, an electromagnetic winding in the delay circuit, and a fourthcircuit, including a resistor shunting said electronic valve so as topermit a controlled inductive voltage rise across the winding upon theopening of said time delay circuit by said switch element so as toeffect an increase in the electrical charge on said capacitor.

6. ln a time delay circuit controlling apparatus of the class includingan electronic valve having an anode and cathode connected in said timedelay circuit and a control grid, a capacitor connected between the gridand the cathode, a circuit for charging said capacitor and a circuit fordischarging said capacitor, said capacitor applying a bias to said gridfor controlling said electronic valve, and an electromagnetic meansconnected in the time delay circuit; the improvement comprising a singleswitch element in the time delay and discharging circuits and operatedby said electromagnetic means to open said last mentioned circuits so asto effect a transfer of said capacitor from the discharging to thecharging circuit upon cnergization of said electromagnetic means, saiddischarging circuit including variable resistance means for retardingthe discharge of said capacitor, and means operably connecting saidelectromagnetic means to said variable resistance means.

7. ln a time delay circuit controlling apparatus of the class includingan electronic valve having an anode and cathode connected in said timedelay circuit and a control grid, a capacitor connected between the gridand the cathode, a circuit for charging said capacitor and a circuit fordischarging said capacitor, said capacitor applying a bias to said gridfor controlling said electronic valve, and an electromagnetic meansconnected in the time delay circuit; the improvement comprising a singleswitch element in the time delay and discharging circuits and operatedby said electromagnetic means soy as to effect a transfer of saidcapacitor from the discharging to the charging circuit upon energizationof said electromagnetic means, and said switch element effective uponsuch energization of the electromagnetic means for directly opening saidtime delay and discharging circuits.

8. In a time delay circuit controlling apparatus of the class includingan electronic valve having an anode and cathode connected in said timedelay circuit and a control grid, a capacitor connected between the gridand the cathode, a circuit for charging said capacitor and a circuit fordischarging said capacitor, said capacitor applying a bias to said gridfor controlling said electronic valve, and electromagnetic meansconnected in the time delay circuit; the improvement comprising a rstswitch element in the time delay and discharging circuits and operatedby said electromagnetic means to open said discharging circuit so as toeffect a transfer of said capacitor from the discharging to the chargingcircuit upon energization of said electromagnetic means, and a secondswitch element effective upon the energization of said electromagneticmeans for shunting said cathode and anode and said first switch elementso as to maintain energization of said electromagnetic means while saidcharging circuit is applied to the capacitor, and means driven by saidelectromagnetic means for returning said second switch element to itsoriginal relationship to effect deenergization of said electromagneticmeans.

9. In a time delay circuit controlling apparatus of the class includingan electronic valve having an anode and cathode connected in said timedelay circuit and a control grid, a capacitor connected between the gridand the cathode, a circuit for charging said capacitor and a circuit fordischarging said capacitor, said capacitor applying a bias to said gridfor controlling said electronic valve, and electromagnetic meansconnected in the time delay circuit; the improvement comprising a firstswitch element in the time delay and discharging circuits and operatedby said electromagnetic means to opensaid discharge circuit so as toeffect a transfer of said capacitor from the discharging to the chargingcircuit upon energization of said electromagnetic means, a second switchelement effective upon the energization of said electromagnetic meansfor shunting said cathode and anode and first switch element so as tomaintain energization of said electromagnetic means while said chargingcircuit is applied to the capacitor, means driven by saidelectromagnetic means for returning said first and second switchelements to the original relationship.

l0, In a time delay circuit controlling apparatus ofthe class includingan electronic valve having an anode and cathode connected in saidtimedelay circuit and a control grid, a capacitor connected between thegrid and the cathode, a circuit forA charging said capacitor and acircuit for discharging said capacitor, said capacitor applying a biasto said grid for controlling said electronic valve, and electromagneticmeans connected in the time delay circuit; the improvement comprising afirst switch element inthetime delay and discharging circuits andoperated by said electromagnetic means to open the discharging circuitand effect a transfer of said capacitor from the discharging to thecharging circuit upon energization of said electromagnetic means, asecond switch element effective upon the energization of said electro-".agnetic means for shunting said cathode and anode and first switchelement so as to maintain energization of said electromagnetic meanswhile said charging circuit is applied to the capacitor, means driven bysaid electromagnetic means for returning said first and second switchelements to the original relationship, and other means driven by saidelectromagnetic means for opening said time delay circuit after apredetermined cycle of operation.

l1. In a time delay circuit controlling apparatus of the class includingan electronic valve having an anode and cathode connected in said timedelay circuit and a control grid, a capacitor connected across saidcathode and grid for applying a bias to said grid for controlling saidelectronic valve, a circuit for charging said capacitor, a cir` cuit fordischarging said capacitor, and a source ot` electrical energy for saidcircuits; the improvement comprising a single switch element in the timedelay circuit and closing said discharging circuit so as to conduct anegative charge to the cathode for closing the time delay circuit, saidcharging circuit controlled by said single switch element, and saidcharging circuit arranged to apply a positive charge to said cathode fordi-ionizing said valve upon said switch element being actuated so as toopen the time delay circuit.

12. A time delay circuit controlling apparatus comprising an electronicvalve having an anode and a cathode connected in said time delay circuitand a control grid, a capacitor for controlling the operation of saidelectronic valve, a source of electrical energy, first `means includingsaid first mentioned electronic valve connected at one side of saidcapacitor and another electronic valve connected at the opposite side ofsaid capacitor so as to serially connect said source in circuit withsaid capacitor for charging the capacitor, second means including adischarge circuit for said capacitor, a switch member alternatelyoperable to open said discharge circuit to make effective the chargingcircuit of said first means and to close said discharge circuit so as toconnect said capacitor in shunt relation to said other electronic valveand said source in circuit with said capacitor to discharge thecapacitor.

13. A time delay circuit controlling apparatus comprising an electronicvalve having an anode and a cathode -connected in said time delaycircuit and a control grid, a

capacitor for controlling the operation of said electronic valve, asource of electrical energy, first means including said first mentionedelectronic valve connected at one side of said capacitor and anotherelectronic valve connected at the opposite side of said capacitor so asto serially connect said source in circuit with said capacitor forcharging the capacitor, second means including a discharge circuit forsaid capacitor, a switch member alternately operable to open saiddischarge circuit to make effective the charging circuit of said firstmeans and to close said discharge circuit so as to connect saidcapacitor in shunt relation to said other electronic valve and saidsource in circuit with said capacitor to discharge the capacitor, and anelectromagnetic winding in the delay circuit for controlling theoperation of said switch member to alternately make effective saidcharging and discharging circuits.

14. A -device of the character described, comprising, in combination, anelectronic valve having an anode, a cathode and a :control grid, saidanode and cathode connected in a control circuit, means applying a biasto said grid for controlling said circuit, motor means operatedperiodically under control of said circuit, a plurality of load devices,switching means actuated by -said motor means to sequentially affectsaid load devices, a manually operable switch means to simultaneouslyrender said motor actuated switching means ineffective and to shunt saidanode and cathode so as to effect independent energizat'ion of saidmotor means, and means actuated by said motor means for opening saidshunt circuit at a predetermined position of the motor means.

15. An electronic timing system for controlling a plurality of externalcircuits in succession comprising means to accumulate an electricalcharge, a charging circuit, a plurality of discharge circuits fordischarging said charge accumulating means at different rates, andswitching means including a plurality of switching elements and anelectro-magnetic winding to operate said switching elements, one of saidswitching elements in the discharging circuit and operated by saidelectromagnetic winding to open the discharging circuit and makeeffective said charging circuit, other of said switching elementsoperable in step-by-step action by said electromagnetic winding inresponse to charging and discharging cycles to effect a repetition ofsaid cycles with said different discharge circuits successively and toenergize said external circuits successively.

16. An electronic timing system for controllingra plurality ,Of externalcircuits in succession comprising means toaccumulate an electricalcharge, a charging circuit including a rectifier lconductive toelectroni-c flow only in a direction for charging said, chargeaccumulating means, a plurality of discharge circuits for dischargingsaid charge accumulating means at different rates, and switching meansincluding a plurality of switching elements and an electromagneticwinding to operate said switching elements, an energizing circuit forsaid electromagnetic winding, one of said switching elements in both theenergizing and discharging circuits, said one switching 'elementoperated by said electromagnetic winding to open both the energizing anddischarging circuits and make the charging circuit effective throughsaid rectifier upon energization of said electromagnetic winding, otherof said switching elements operable in step-by-step action by saidelectromagnet winding to effect a repetition of said cycles with saiddifferent discharge circuits successively and to energize said externalcir-cuits successively.

17. A time delay circuit controlling apparatus comprising, an electronicvalve for controlling said circuit, a capacitor for controlling theoperation of said electronic valve, an electromagnetic means in the timedelay circuit controlled by the electronic valve, a switch member in thetime delay circuit, said switch member alternately opened and closed bysaid electromagnetic meansa charging circuit for said capacitoreffective upon the opening of the time delay circuit by the switchmemberand a discharging circuit for said capacitor effective upontheclosing of the time delay circuit by said switch member, a source ofelectrical energy for said 14 circuits, said charging circuit includingunidirectional conductive means, and said switch element in said timedelay and discharging circuits and arranged to connect said capacitor inshunt relation to said unidirectional conductive means for dischargingsaid capacitor.

18. For use with an apparatus for controlling a plurality of cyclicallyoperable inflatable ice removing elements on airfoil surfaces of ansaiucraft; the combination comprising electrical control means fortiming the period of inflation of each of the ice removing elements,electric light means adapted to be connected to a source of electricalenergy, means operated by said control means to periodically connectsaid electric light to said source means for visually indicating theinterval of inllation of each ice removing element, and manuallyoperable switch means for selectively connecting said light means tosaid operated means to indicate said intervals of inflation and acrosssaid source for indicating the electrical condition of the source.

19. For use with an apparatus for controlling a plurality of cyclicallyoperable inflatable ice removing elements on airfoil surfaces of anaircraft; the combination comprising electrical control means for timingthe period of inflation of each of the ice removing elements, electriclight means adapted to be connected to a source of electrical energy,switch means operated by said control means to selectively connect saidlight means to said source for visually indicating the interval ofinflation of eachice removing element, other electric light means, saidswitch means operated by said control means to selectively connect saidother` light means to said source for visually indicating the period ofinoperation of said elements between cycles ot operation, additionalelectric light means for.. visually indicating the electrical conditionof the source, and other switch means cooperating with said firstmentioned switch means for connecting all of said indicator lightmeanstosaid source, said other switch means manually yoperable to place saidindicator light means out of operation irrespective of the operativecondition ofsaid control means. l

2,0. For use with an apparatus for electrically controlling a pluralityof cyclically operable inflatable ice removing elements for airfoilsurfaces of an aircraft; the `combination comprising a unitary housing,a plurality of electric lights carried in said housing, first circuitmeans for electrically connecting said lights to said apparatus forvisually indicating the indivudal interval of ination of each iceremoving element, another electric light carried in saidhousing, secondcircuit means for electrically connecting said light to said apparatust'or visually indicating the period of inoperation of said elem-entsbetween cycles of operation, an additional electric light, third circuitmeans for electrically connecting said additional lightto a source of'electrical energy for said apparatus for visually indicating theelectrical condition of the control apparatus, and a manually operablecontrol switch means in said ilrst, second and third circuit means forconnecting said indicator lights to said source, said control switchmeans manually operable to open said circuits to place said indicatorlights out of operation irrespective of the operative condition of saidcontrol apparatus.

2l. An electronic timing system for controlling a plurality of externalcircuits in succession comprising means to accumulate an electricalcharge, a charging circuit, a plurality of discharge circuits fordischarging said charge accumulating means at different rates, anelectronic Vvalve having an anode, cathode andcontrol grid, a circuitincluding said anode and cathode, said grid biased by the chargeaccumulating means to control the current in said anode-cathode circuit,said charging circuit including means conductive to electronic flow in acharging direction only, control means for terminating the electron flow`through said conductive means, switching elements operable instep-bystep action to effect said diiferent discharge circuitssuccessively and to energize said external circuits successively, andcurrent responsive means in the anodecathode circuit, saidlast-mentioned means directly controlled by the current in theanode-cathode circuit for eiecting the operation of said control meansand the aforesaid operation of said switching elements in response tothe charging and discharging cycles.

22. The combination dened by claim 2l in which said conductive meansincludes a second electronic valve having an anode and a cathodeconnected in the charging circuit.

23. The combination defined by claim 2l in which said current responsivemeans includes an electromagnetic winding in the anode-cathode circuitfor operating the switching elements in the step-by-step action.

24. The combination deiined by claim 2l in which said conductive meansincludes a second electronic valve having an anode and a cathodeconnected in the charging circuit, and said current responsive meansincludes an electromagnetic winding in the anode-cathode circuit of thefirst-mentioned electronic valve for operating both the control meansand the switching elements.

25. In a time delay control the combination with a condenser, anelectromagnetic relay having an operating winding and operative to pickup and to drop out at predetermined current values respectively in saidwinding, a tirst circuit for initially connecting said winding across asource of unidirectional voltage for energizing said winding at the pickup current value of said relay, and a second circuit for seriallyconnecting said condenser and said winding across said source ofunidirectional voltage for charging said condenser, of means foralternately effecting operation of said iirst and second circuits, aby-pass circuit connected in parallel with said condenser to provide anadditional path for current flowing to said winding, the sum of thecurrents flowing to said winding through said second circuit during thecharging period of said condenser and through said by-pass circuit beinggreater than the drop out current value of said relay, and a resistor insaid by-pass circuit, the resistance of said resistor and of said relaywinding being so related to the voltage of said source that the currentflowing through said bypass circuit operatively increases the uxproduced by said winding while remaining below the drop-out currentvalue of said relay.

26. A time delay control comprising an electronic flow resistance means,a switch operable when closed to connect one end of said resistancemeans to one side of a source of direct current, a condenser, meansconnecting said condenser between said one end of said resistance meansand the one side of said source of current, a resistor connected betweensiad one side of said source and the other end of said resistance means,an electromagnetic device having an operating winding connected betweensaid other side of said source and said other end of said resistancemeans, said winding when energized operating said device to open saidswitch so as to cause charging of said condenser by said source ofcurrent through said resistance means and operating winding, the sum ofthe current flowing to said winding from said condenser and the currentflowing to the winding through said resistor during the charging of saidcondenser' is snticient to hold said device in operated position whereasthe current flowing to said winding through said resistor is insucientof itself to hold said device in operated position.

27. A recycling timing apparatus comprising a condenser, relay means, anelectron discharge device having said condenser connected to the inputthereof and said relay means in the output thereof, a source of controlvoltage, circuit means for connecting said condenser to said source tocharge said condenser` impedance means in said charging circuit fordelaying the charging of said condenser through a tirst time interval,said relay means when energized by said discharge device effectingoperation of said circuit means to charge said condenser for said firsttime interval, said condenser when approaching a maximum chargedcondition rendering said discharge device and thereby said relay meansinoperative, means actuated by said relay means when inoperative toconnect said condenser in a discharging circuit, impedance means in saiddischarge circuit for-delaying the discharge of said condenser-through asecond time interval until said discharge device becomes operative toenergize said relay means and thereby restart the rst charging interval.

28. A recycling timing apparatus comprising a condenser, relay means, anelectron discharge device having an anode, cathode and controlelectrode, means connecting said condenser to said control electrode andsaid re- Ylay means in energizing relation to said anode, a source ofdirect current control vo-ltage, circuit means including an electricalresistance means for connecting said condenser to said source to chargesaid condenser, said relay means controlling said circuit means, saidrelay means when energized by said discharge device rendering saidcircuit means effective to charge said condenser through a tirst timeinterval until said control electrode renders said discharge deviceinoperative whereupon said relay means becomes de-energized, meansactuated by said relay means when de-energized to connect said condenserin a discharging circuit, means connected in said discharge circuit fordelaying the discharge of said condenser through a second time intervaland until the voltage thereon renders said discharge device conductiveto energize said relay means and thereby restart the charging ofsaid-condenser for the first charging interval, said discharge devicecontinuing conductive throughout the charging interval, and means forconnecting said cathode to said source while said condenser isdischarging during the second interval so that said control electrodewill tend to go to a potential that is positive with respect to saidcathode.

29. A recycling timing apparatus comprising a timing condenser, relaymeans, an electron discharge device having an anode, cathode and controlelectrode, said timing condenser being connected between said cathodeand said control electrode and said relay means being connected inenergizing relation to said anode, a source of direct current voltagehaving positive and negative terminals thereon, circuit means forconnecting said condenser Vbetween opposite positive andnegativeterminals on said source to charge said condenser so as to applya negative bias to said control electrode, said circuit means includingimpedance means delaying the charging of said condenser, said relaymeans when energized by said discharge device rendering said circuitmeans etfective to charge said condenser until the negative bias on saidcontrol electrode increases to a value suicient to render said dischargedevice inoperative whereupon said relay means becomes de-energized,means actuated by said relay means when de-energized to connect saidcondenser in a discharging circuit and render said charging circuitmeans ineffective, means for effectively connecting said cathode to anegative terminal on said source while said condenser is dischargingthrough said discharge circuit so that said control electrode will tendto go to a potential that is positive with respect to said cathode,means connected in said discharge circuit for delaying the discharge ofsaid condenser until the negative bias on said control electrodedecreases to a value sufficient to render said discharge deviceconductive for energizing said relay means so as to render said chargingcircuit means effective to charge said condenser, and said dischargedevice continuing conductive during the charging interval of thecondenser.

30. The combination dened by claim 27 including a by-pass circuitconnected in parallel with said condenser to provide an additional pathfor supplying current to said relay means, said relay means beingenergized and de-energized at predetermined current values, the sum ofthe currents owing to said relay means through said discharge device andsaid by-pass circuit during the charging of said condenser being greaterthan said energizing current value of said relay means so as to maintainthe relay means energized when the current ilowing to said relay meanssolely through said discharge device falls below said energizing currentvalue, a resistor in said bypass circuit, the resistance of saidresistor being so related to the voltage of said source that the currentflowing through said by-pass circuit increases the current to said relaymeans while remaining below the energizing -current value of said relaymeans.

31. The combination of means for applying a resultant potential havingpositive and negative components, a relay, `an energizing circuit forsaid relay, a resistor, a capacitor, circuit control means operable toapply said negative component to said capacitor in response toenergization of said relay and to apply said positive component throughsaid resistor to said capacitor in response to deenergization of saidrelay, and means operable to deenergize said relay only While the chargeof said capacitor is Within a range extending from its most negativevalue to approximately zero.

32. The combination of means for applying a resultant potential havingpositive and negative components, a relay, an energizing circuit forsaid relay comprising a gaseous conduction device provided with acontrol grid and an anode and cathode and connected to have saidpositive component applied through said relay between its anode andcathode, a capacitorv connected between said cathode `and grid, meansfor interrupting the current of said gaseous conduction device, aresistor, and circuit control means responsive to operation of saidrelay for applying said negative component to said capacitor in responseto current conduction of said gaseous conduction device and for applyingsaid positive component through said resistor to said capacitor inresponse to interruption of said current conduction.

33. An electronic sequence timer including at least one electricdischarge device for controlling the sequencing of said timer, saiddevice having associated therewith a timing network which when set timesthe operation of said device; characterized by a single controldischarge device having conductive and non-conductive states connectedin circuit with said network; means responsive to said control devicewhen it passes from one state to the other to set said network and meansresponsive to said device when it passes from said other state to saidone state to initiate the timing operation of said network.

34. In combination, a iirst electric discharge device having an anode, acathode, and a control electrode; means including a capacitorcooperative with said control electrode and including a timing networkwhich when set maintains said device in non-conductive condition duringan interval in which the capacitor discharges and which timing networkafter a predetermined time interval renders said device conductiveduring an interval in which the capacitor charges; a second electricdischarge device;

means for maintaining said second device non-conductive during theinterval in which the capacitor discharges; means for rendering saidsecond device conductive; means cooperative with said timing means andsaid second device for setting said timing means when said second deviceis rendered conductive and means for thereafter rendering said seconddevice non-conductive to initiate the timing of said timing means.

35. An electronic timing device comprising means for supplying anenergizing current and biasing voltage, an electron valve -havingcontrol grid, cathode and anode electrodes, a relay connected in seriesbetween said anode electrode and said current supply means, said relayoperating responsive to flow of current in said valve, a chargingcircuit comprising a condenser and resistor in series, said condenserbeing connected between said control grid electrode and said cathodeelectrode, and means for connecting both said condenser and said controlgrid electrode to said biasing voltage supply means upon operation ofsaid relay.

36. A timing device comprising a source of electrical energy; a tube ofthe electronic valve type with anode, cathode and control electrode;means to connect a controlled electromagnetic winding in series withsaid anode and cathode; a resistor and means to connect said resistoryacross said cathode and anode, said resistor providing means forcontrolling the inductive voltage rise across the electromagneticwinding when said tube is non-conductive with the electromagneticWinding and resistor in series; and means to connect said anode andcathode to said source of electrical energy and to bring said controlelectrode to ring potential.

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